Sighting device for aircraft



Marl 27, 1923 1,449,526

0. MACKENSEN SIGHTING DEVICE FOR AIRCRAFT Filed Aug. 15, 1921.

Patented Mar. 27, I923.

imam

QTTO MACKENSEN, F J'ENA, GERMANY. ASSIGNOR TO THE FIRM or CARL ZEISS, or

JENA, GERMANY.

SIGHTILIG DEVICE FOR AIRCRAFT.

Application filed August 13, 1921. Serial No. 492,110.

To all whom it may concern:

Be it known that I, OTTO MACKENSEN, a citizen of the German Empire,residing at Jena, Germany, have invented a new and 5 useful SightingDevice for Aircraft, of

which the following is a specification.

The present invention relates to a device, provided with a downwardlydirected sighting device, the sight line of which, by means of anadjustable gearing (e. g. a curve-gearing), actuated by a uniformlyrunning driving gear (e; gfclock work), undergoes a change ofinclination and which device serves for determining the moment ofdropping projectiles from air-crafts,'i. e. that moment when the sightline reaches that position in Which the angle, embraced by it and theVertical line, is equal to the dropping angle.

In the annexed drawing Fig. 1 is a diagrammatic view showing theschematic principles of the invention. Figs. 2 and 3 are verticalsections through a device according to the invention.

Fig. 1 of the said drawing may serve to elucidate the principle of theinvention. AC

denotes the trajectory of an air-craft, moving along at the height H atthe speed 1:.

According to the air-craft being at A or B or C, the sight-line directedtowards a target Z is inclined towards the vertical line at an angle qor a, or zero. Let the angle a be the aiming ofi' angle. In order thatthe sight-line will always remain directed at the target, it isnecessary to change the angle p constantly, viz. according to theequation, easily to be derived The dropping angle a is determined by theequation 'U'r R in which case 1: means the time, required by aprojectile for dropping from'the height H, and R denotes the back-driftwhich the projectile undergoes during this drop owing to the resistanceof the air in the direction of flight, As the time required for droppingcos g0 '40 on the other hand, the

is a function of the height H and as, furthermore, the value K may betaken as invariable for a certain shape of the projectile and anunchangeable actual speed of the aircraft, the equatlon 2 may bereplaced by e f From the two equations 1 and 3 it follows that for acertain value of the fraction .in such a manner that the sight-lineremains automatically directed to a target to which it has been directedat the outset. Besides, the said gearing is so constructed that to eachvalue of the fraction corresponds a certain adjustment.

The adjustment of the gearing, which'corresponds to the value of thisfraction in each case, is suitably ascertained by means of trials, i. e.by being altered until the sightline remains directed to the target. Onthe other hand, according to the invention the gearing is coupled to asecond gearing, serving for the adjustment of the dropping angle in sucha manner that the said second gearing only-needs an adjustment by handin accordance with the height of flight H of the air-craft.

In order to make known the moment of dropping, any suitable arrangementmay be made, e. g. the motions of the sight line (the alterations of theangle qa) may, in a known way, be indicated by an index on a scalegraduated according to angular values, the dropping angle a beingindicated by a second index 0n the said scale.

However, such an indicator-device may be dispensed with, if provision bemade for an automatic release of the projectile dependent on thedropping angle and the position of the sight-line.

The advantage afforded by a device, equipped according to the invention,over other devices of this kind consists in the fea ture, that on theone hand, the sight-line re' mains automatically directed to a targetand that, on the other hand, owing to the two gearings being coupled toeach other, the dropping angle can be ascertained in a particularlysimple Way.

If a sighting telescope be used as a sighting device, it is advisable,with a View to attain the largest possible inclinations of the sightline towards the perpendicular line, to dispose the sighting-mark of thetelescope unadjustably and to effect the ad-.

justment of the sight-line by rotating a reflector system, disposed infront of the objective.

An advantageous kind of construction may be attained by providing eachofthe two gearings with a cam, viz, the gearing actuated by the drivinggear with a cam which is uniformly rotated by the driving gear andadjustably disposed in the, direction of its axis of rotation accordingto the fraction v ing serving for the adjustment of the dropping angleWith a cam, disposed in such a Way as to be able to undergo twoadjusting motions, viz, on the one hand, a rotation and, on the otherhand, a displacement in the direction of its axis of rotation, one ofthese motions taking place automatically, owing to the two gearingsbeing coupled to each other, when adjusting the cam-appertaining to theother gearing.

In order to be able to alter quickly the inclination of the sight-linewithin wide limits, without impairing the motion given to the sight-lineby the driving gear which, e. g.', is desirable in order to require, incase of an intended change of the target after having regulated thedrive of the sight-line, another regulation of the said drive, thedriving gear may be fixed to a rotatably supported bushwhich forms thebearing for the cam adjustin the sight-line and the axis of rotation 0which coincides with that of the said cam; a rotation of the bushthen'results in another rotation of the cam, independent of the rotationeffected by the driving gear. a

igs. 2 and 3 of the annexed drawing show a device according to theinvention in which a sighting telescope is used as a sighting device.Fig. 2 is a vertical section of the device which contains the opticalaxis of the telescope and Fig. 3 is another vertical section. I

The telescope is a terrestrial one. Of its and the gear-'.

objective are visible. The said prism system is composed of twoisosceles, rectangular prisms, one of which, a is rigidly disposed inthe casing a, whilst the other afimediating the entrance of light, is sodisposed in a bush 6, rotatably sup orted 'in the casing a, the axis ofrotation of which bush intersects the optical axis of the telescope andwhich is vertical to the plane -containing the optical axis, that therefiecting surface of the said prism contains this axis of rotation. Therigidly disposed prism a is connected to another isoscele, rectangularprism a? in such a manner that the hypotenusal surfaces of both prismscoincide, thus allowing of observing at the same time asighting mark 0,traced upon a glass plate 0 with an object visible by means of the prisma The said sighting mark is supported after the Garden principle in sucha way that the centre of the bearing coincides with the front princi;pal point of a collective lens g3 and that its distance from thesighting mark is equal to the focus of the said collective lens so thatthe sight-line determined by the sightingmark is always verticallydirected.

The inclination of the ray,of the sight-, line can be varied by arotation of the bush 6. Such a rotation is effected by raising andlowering a wire 6, actuating at its bottom and a yoke e, the two arms ofwhich are connected by means of a joint to one each of two arms I) fixedto the bush 6. Besides, a spring 6 fitted to the casing a and to thebush 1) always tends to bring the latter into that terminal position, inwhich the position of the prism a corresponds to the largest amountofaiming off of the sight line. The raising and lowering of the said wire6 is effected by a rotation of a lever f actuating at the top end of thewire, the said lever being wedged to a shaft f, rotatably supported onthe vcasing a. The said shaft is actuated bya rotation of the bell crankf i the one arm of which f is fixed to the shaft 7" whilst the other fis in' contact with a cam g. The latter is rotatably supported in asupport h, slidably mounted between two guide members a on the casing a.and displaceable parallel to the chief axis of the telescope, in such amanner that its axis of rotation is parallel to the direction ofdisplacement of the supporting body. The

casing i contains a clockwork of which the shaft is denoted i and thewinding-up button by j and which by means of a shaft i gives the cam g,a uniform, when viewed from above, counterclockwise rotation. Witha'displacement of the support it the shaft 1' may slide along a spring 9of the cam by a groove i The clockwork casing i is fixed to a bush is,rotatably disposed at the 5 ing of a second cam 7,

casing a, the axis of rotation of the said bush coinciding with that ofthe cam This bush forms the bearing of a shaft l, which may be rotatedby means of a knob Z and on which a toothed wheel Z is fastened engagingin a circular rack 72, of the support it, the teeth of the said gearingrunning round the said body lb. The cam g is constructed in such a way,that in its highest position, corresponding to the largest, adjustablevalue of the uotient from the speed and the height of flight oftheaircraft, viz, the fraction with a complete revolution by means of theclockwork such a rotation of the prism a is effected, that the angle ofinclination of the sighting ray towards the vertical lineo varies fromabout to 0. In the lowest position of the cam, corresponding to thesmallest, adj ustable value of the said quotient, an alteration of thisangle Q from about 40 to 0 takes place. To the value of the angle (9adjusted in each case corresponds a certain position of the arm 17?) ofa bell crank m m which is rotatably disposed on the casing 01. about anaxis parallel to the shaft 7 in such a manner, that the free end of thearm m will be visible through the ocular of the sightingtelescope. j Thebell crank is adjusted with the aid of a lever f fixed to the shaft 7",with which its arm m is in contact by means of a slit guide. The supporth also forms the bearwhich participates in the same way as the cam g isthe displacements of the support k and which is so disposed as to engageby a groove n? in a spring 0, fixed to a rota-tably disposed shaft 0 theaxis of rotation of which coincides with that of the cam g, and alongwhich it may slide when the support it is displaced. The shaft 0 can berotated by means of a driving knob '0 and an index 0 indicates the valueof the rotation on a scale a graduated according to heights of flight.The cam n is connected with the arm 70 of a bell crank p 12 the arm 39being fixed to a shaft 12,Which is parallel to the shaft 2 and rotatablysupported on the casin a. oreover, the cam n is so constructed t at,when being placed into such a position that the index 0 indicates on thescale a the height of flight H in each case and the adjustment of thesupport. It corresponds to the value of the fraction in eachv case,

the position of the shaft p corresponds to the dropping angle a,required for'dropping a projectile at the said speed a and the saidheight H of the air-craft. To the value adjusted ineach case of thedropping angle a corresponds a certain position of the arm 9 of a bellcrank g 9 which similar to the angle lever m m is rotatably disposed onthe casing a about an axis parallel to the shaft p in such a manner thatthe free end of the arm 9 will also be visible through the ocular of thesighting telescope. The bell crank 9 g is adjusted by means of a lever pfixed to the shaft 12", with which its arm 9 is connected by a slitguide. The arms m and g of the two angle levers are disposed closetogether so that, the relative position of their free ends can beobserved.

In'the annexed drawing the single parts of the device assume a positioncorrespondt "to an angle q) of the sighting ray relative to the verticalline of 0 and to a dropping angle a of about 20. In order to be used,the device must be fixed to an air-craft in such a manner that with ahorizontal position of the air-craft its chief axis is verticallydirected. Thereupon the clockwork is to be actuated, and by rotating thebush 9 and ing t'ovan average value of the fraction is about its axis ofrotation the cam at the same time the prism a should be adjusted in sucha manner that the image of the sighting mark 0 coincides with that of atarget to be hit by a shell and, moreover, it is necessary to adjust thesupport it, by rotating the driving knob Z in such a way that these twoimages also remain coincident. By then adjust-ing with the aid of thedriving knob 0 the cam n in such a manner that the index 0 indicates theheight of flight of the air-craft on the scale a and consequently thearm 9 of the bell crank 9 9 assumes the position corresponding to therequisite dropping angle it will only be necessary to observe when thefree end of the arm m of the bell crank m m coincides with that of thearm 9 At the moment when the arm m has reached the said position, theprojectile should be dropped.

I claim:

1. In a downwardly directed sighting device for air-crafts an adjustablegearing,

a uniformly running driving gear actuat-- ing this gearing, part of thesighting device beingmovable and adapted to affect the position of thesight line of the device, means for connecting the said gearing to thesaid movable part, the latter part, on being adjusted according to theheight of flight and speed in each case, being adapted to keep the sightline automatically directed to the target, and means for coupling thesaid gearing to anotherone adapted to adjust the dropping angle in orderto change automatically the position of the said gearing, when adjustingthe said first gearing, in such a way as to require only one adjustmentby hand according to the height of flight of the air craft.

2. In a downwardly directed sightingdevice for air-crafts an adjustablegearing, a uniformly running driving gear actuating this gearing, a camundergoing a uniformly revolving motion by the said driving gear andbeing adjustable in the direction of its axis of rotation, the saiddriving gear being fixed to a bush rotatably supported on the carrierofthe said sighting device and serving as a bearing of the said cam 50that,

on the bush being rotated, both the cam and 10 the driving gear arerotated as Well and that the cam undergoes a further rotation,independent of that effected by the said driving gear.

OTTO MACKENSEN. Witnesses 2 L I 1 PAUL KRt'IGER, RICHARD HAHN.

